This knob is designed for 2007-2011 MasterCraft boats with a factory Zero Flex Flyer (ZFT3) tower. This tower and knob can be found on the following models of MasterCraft boats: X-1, X-2, X-7, X-9, X-15, X-25, X-30, X-35, X-45 and X-55. This knob is located on the front leg at the "pivot" where the tower leg folds in front of the windshield and into the bow. This knob is often removed when lowering a tower to fit into a garage or under a canopy. Includes nylon washer. Solid metal construction for long lasting durability. This MasterCraft tower knob is designed to tighten by hand and features a textured design to ensure easy installation and removal. This knob is commonly miss placed or dropped to the watery depths! Plan ahead and keep a spare.